In the 3rd Generation Partnership Project (3GPP), which is a standardization project for a mobile communication system, the introduction of terminal-to-terminal (Device to Device: D2D) communication is considered as a new function launched from the release 12 (refer to Non Patent Literature 1).
In D2D communication, direct terminal-to-terminal communication is performed not via a network, within a terminal group including a plurality of closely-located user terminals. On the other hand, in cellular communication, which is normal communication of a mobile communication system, a user terminal performs communication via a network.
In the D2D communication, since radio communication with low transmission power can be performed between closely-located user terminals, the power consumption of the user terminals and the load on the network can be reduced as compared with the cellular communication.